Vol. 6(5), pp. 24-30, June 2015 DOI 10.5897/JCO15.0135 Article Number: F1B7EF453767 ISSN 2141-6591 Copyright ©2015 Author(s) retain the copyright of this article http://www.academicjournals.org/JCO
Journal of Cereals and Oilseeds
Full Length Research Paper
Yield, quality, kinetics and thermodynamics studies on extraction of Thevetia peruviana oil from its oil bearing seeds J. M. Jabar1*, L. Lajide1, A. O. Adetuyi 1, B. J. Owolabi1, I. O. Bakare2, T. G. Abayomi3 and A. L. Ogunneye4 1
Chemistry Department, School of Sciences, The Federal University of Technology, Akure, Ondo State, Nigeria. End-Use Division, Rubber Research Institute of Nigeria, P. M. B. 1049, Benin City 300001, Edo State, Nigeria. 3 Chemical Science Department, Faculty of Science/Adekunle Ajasin University, Akungba Akoko, Ondo State, Nigeria. 4 Petroleum and Chemical Science Department, Tai Solarin University of Education, Ijebu-Ode, Ogun State, Nigeria. 2
Received 25 November 2014; Accepted 28 April 2015
The present research shows possibility of extracting Thevetia peruviana oil from its oil bearing seeds by cold and soxhlet extraction methods, using petroleum ether as extracting solvent at room temperature and 40 to 60°C respectively. Characterisation of the oil showed that the percentage oil yield, acid value, saponification value and viscosity increased as temperature of soxhlet extraction increased, while the specific gravity and iodine value of the extracted oil decreased at high temperature of extraction in soxhlet extraction method. Cold extraction showed improved quality and oil yield, in comparison with oil obtained from soxhlet extraction method. The kinetics of the oil extracted from soxhlet extraction method was derived from mass transfer rate equation and was found to fit well with only pseudo-second order kinetic of volumetric mass transfer rate coefficient 0.04 h -1. The thermodynamics study of the extracted oil showed that ∆H and ∆S were positive while ∆G was negative, indicating that T. peruviana oil extraction process was endothermic, spontaneous and irreversible with exception to extraction at 40 and 45°C. Key words: Extraction, irreversible, kinetic, thermodynamic, quality. INTRODUCTION There are two varieties of the oleander plant; both belong to order apocynales of apocyanaceae family (Sahoo et al., 2009). One with yellow flowers is called yellow oleander (Thevetia peruviana), and the other with purple flowers is known as nerium oleander (Thevetia nerrifolia) (Usman et al., 2009). T. peruviana is a native of tropical America; especially Mexico, Brazil and West Indies and has naturalized in tropical regions worldwide. In the
native countries it is believed to be more than 2000 years old and known as yellow oleander, gum bush or milk bush, exile tree, olomi ojo in India, Cabalonga in Puerto Rico, Ahanai in Guyana and Yoruba in Nigeria respectively (Sahoo et al., 2009). In Nigeria, T. peruviana has been grown for over fifty years as an ornamental plant in homes, schools and churches (Usman et al., 2009; Ibiyemi et al., 2002), flowers and fruits all year
*Corresponding author. E-mail:
[email protected]. Tel: +2348062423910. Author(s) agree that this article remain permanently open access under the terms of the Creative Commons Attribution License 4.0 International License
Jabar etal.
round, providing steady supply of seeds from fruits of between 400 to 800 per annum depending on the rainfall pattern and plant age (Usman et al., 2009; Balusamy and Manrappan, 2007), each of the fruits contains between one to four seeds of oil content 60 to 65% in its kernel (Mohibbe et al., 2005). Despite the fact that there is high level of oil in the seed, it remains non–edible because of the presence of cardiac glycoside (toxins) (Usman et al., 2009), as a result of this, T. peruviana oil is not used as food but used in industrial production of insecticides, lubricant, bio-diesel, soap, cosmetics, paints, polyol etc (Kareru et al., 2010). The three common methods by which T. peruviana oil is extracted from its oil bearing seeds are; mechanical pressing, supercritical fluid extraction and solvent extraction (Liauw et al., 2008). Industrial extraction of the oil from its seeds is commonly done by mechanical pressing, but the oil obtained from this method usually contain a high percentage of water, metal content and its turbid nature result in low market price (Adeeko and Ajibola, 1990). Highly purified oil is obtained from supercritical fluid extraction method, but has a demerit of high operating cost (Mongkholkhajornsilp et al., 2005). Solvent extraction method gives higher percentage yield and less turbid oil than mechanical extraction and a low operating cost in relation to supercritical fluid extraction method (Herodez et al., 2003; Khraisha, 2002). In this research, we used soxhlet and cold extraction (both are solvent extraction) methods to extract T. peruviana oil from its oil bearing seeds using petroleum ether as extracting solvent. The effect of temperature on extracted oil was studied; kinetics and thermodynamics of the soxhlet extraction process were also investigated. MATERIALS AND METHODS Raw material T. peruviana seeds were collected from Aule in Akure south local government area of Ondo state, Nigeria in March 2012.
Pre-treatment of material Seed coats were removed from seeds using hammer, before sun drying for 15 days to obtain moisture free seeds. After sun drying, dirt-like particles were removed from the seeds and the seeds were oven dried at 60°C for 5 h before they were ground with blender. T. peruviana oil was extracted from a known weight of its oil bearing seeds using two different solvent extraction methods, which are cold and soxhlet extraction method.
Cold extraction method A known weight of ground seeds was tightened in a filter cloth before immersing in a metal container containing petroleum ether as extracting solvent with liquor ratio 1:5 and extraction was carried out at room temperature for 7 days. At the end of the extraction time, the extracted oil-solvent mixture was collected, distilled and evaporated to obtain solvent-free oil. The obtained solvent-free oil
25
was weighed to calculate the percentage yield.
Soxhlet extraction method A known weight of ground seeds was placed in the thimble of the soxhlet apparatus, while petroleum ether (extracting solvent) was placed in a 500 ml round bottom flask and extraction was carried out with liquor ratio 1:5 at 40, 45, 50, 55 and 60°C for 4 h each. At every hour interval, the extracted oil-solvent mixture was collected, distilled and evaporated to obtain solvent-free oil. The obtained solvent-free oil was weighed to calculate the percentage yield.
Extraction kinetics and thermodynamics Mass transfer kinetic model was used to study the extraction process, since there was no reaction between the extracting solvent (petroleum ether) and Thevetia peruviana oil (Liauw et al., 2008). The affinity of the oil for the extracting solvent from the oil bearing seeds was determined using Van’t Hoff model, as described by Baba et al. (2011)
Physico-chemical properties of the oil The physico-chemical properties, like acid value (Cd 3a- 63), specific gravity (Ta 1b-64), saponification value (Cd 3–25), iodine value (Cd 1–25), peroxide value Cd 8 –53, refractive index Cc 7 – 25 (09), and viscosity was measured using Abe viscometer at room temperature (Firestone, 2009).
RESULTS AND DISCUSSION Physicochemical properties of extracted oil The effect of extraction temperature on physico-chemical properties of T. peruviana oil is shown in Table 1. In soxhlet extraction method, higher extraction yield was achieved at higher temperature, which reduced the oil viscosity thereby releasing oil from intact cells and also reduced moisture in the cells. This observation agreed with the findings of Liauw and co workers in extraction of neem oil using n-hexane and ethanol (Liauw et al., 2008). This high percentage yield shows that T. peruviana oil has a good potential in the production of oleochemical that can serve as an alternative substitute to high cost ever depleting, non-biodegradable, non-renewable petrochemical resource as concluded by Odeomelam (2005), in proximate composition and selected physicochemical properties of African oil bean (Odeomelam, 2005). In contrary to soxhlet extraction, cold extraction (at room temperature) method gave a better oil yield in comparison with yield from soxhlet extraction as shown in Table 1. The quality of the extracted T. peruviana oil decreased with increase in temperature. This is shown in Table 1, where the acid, free fatty acid, saponification, peroxide value, viscosity and refractive index increased as extraction temperature increased, while the specific gravity and iodine value decreased as the extraction temperature increased, these observations agreed with
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J. Cereals Oilseeds
Table 1. Physicochemical properties of cold and soxhlet extracted T. peruviana oil at different temperature.
Extraction temperature (°C) Oil yield (%) Moisture content (%) 3 Specific gravity (g/dm ) Acid value (mgKOH/g) Free fatty acid (mgKOH/g) Saponification value (mgKOH/g) Peroxide value (mg/Kg) Iodine value (g/100g) Refractive index Viscosity (mPa. s)
Room temp. 63.5 0.10 0.922 7.50 3.75 162.43 3.52 106.00 1.440 154.88
40.0 45.9 0.09 0.921 7.80 3.90 169.73 4.03 92.42 1.442 162.92
Khraisha (2002), in retorting of oil shale followed by solvent extraction of spent shale: experiment and kinetic analysis (Khraisha, 2002). Acid value is an indication of level of free fatty acid formed from hydrolytic decomposition of glycerides to free fatty acid (Abayeh et al., 2011), that was been accelerated by increased in T. peruviana oil extraction temperature as shown in Table 1. Increase in level of free fatty acid caused by increase in extraction temperature was an indication of reduction in quality of the oil in terms of edibility (Adelaja, 2006). The acid values obtained showed that T. peruviana oil is good as starting material for production of paints and varnishes according to the findings made by Abayeh et al. (2011), in quality characteristics of pumpkin seed oil (Abayeh et al., 2011). Average molecular weight of the oil is indicated by saponification value, increase in saponification value with temperature of extraction (Table 1) showed that as temperature of extraction increased, the average molecular weight of the oil reduced, due to breaking down of oil to higher proportion of lower molecular weight fatty acid. The saponification value of Thevetia peruviana (Table 1), showed that the oil is an effective raw material in the soap industry in disagreement with Akanni et al. (2005), in physicochemical properties of some nonconventional oil seeds (Akanni et al., 2005). Oxidative stability of the oil can be determined by its peroxide value, in this extraction process, peroxide value increased with increase in temperature and as a result, the quality of the oil reduced with increase in temperature of extraction, because those extracted at higher temperature are liable to go rancid faster than the one extracted at room temperature of 30°C. The peroxide value obtained in this extraction process is lower than the value between 20 to 40 mg/g at which oil becomes unstable with offensive odour in storage (Jauro et al., 2011), this mean that Thevetia peruviana oil extracted at room temperature (cold extraction) is more stable than those extracted at higher temperature (soxhlet extraction) and all of them not easily deteriorate in storage according to Jauro et al. (2011), in extraction and characterisation
45.0 50.1 0.09 0.918 7.90 3.95 174.36 4.04 88.56 1.442 169.28
50.0 54.8 0.09 0.916 8.10 4.05 179.46 4.06 85.25 1.444 171.84
55.0 58.1 0.08 0.912 8.30 4.15 183.65 4.10 82.08 1.447 177.06
60.0 62.2 0.08 0.908 8.30 4.15 186.25 4.12 79.21 1.448 185.50
of Pentaclethra macrophylla seed oil (Jauro et al., 2011). Viscosity, specific gravity and refractive index of the extracted oil fall within the range of other nonconventional oil and their values increased as extraction temperature increased, with exception to specific gravity (Table 1), this agreed with a report on extraction of oil from water melon seed and analysis (Sodeke, 2005). The iodine value is a measure of unsaturation of triglyceride oil (Gunstone, 2004) and the values obtained in this study ranges from 79.2 to 106.0 g of I2/100 g. Table 1 showed that iodine value of extracted T. peruviana oil decreased with increase in temperature of extraction process. Hence, the oil became less reactive, this is because increase in temperature initiated the breakdown of C = C unsaturation of the oil to C – C saturated carbon chain. The iodine value of T. peruviana oil reported here is within the range of semi drying oil, this showed that it is a potential raw material in paint, lacquer, resin, polyol, grease, lubricating oil and diesel production as stated in the findings made by Eromosele et al. (1998), in studies on seeds and seed oils (Eromosele et al., 1998). Extraction kinetics The T. peruviana oil and the extracting solvent (petroleum ether) are organic materials, this natural similarity made it possible for the oil to migrate into the solvent from the cake cementing it to the ground seeds. Since there was no reaction between the extracted oil and the extracting solvent, the obtained experimental data in soxhlet extraction method were treated using mass transfer kinetic model (Liauw et al., 2008). The first kinetic model The first kinetic model named pseudo first-order kinetic assumed that, the concentration of the extracted oil is directly proportional to the mass transfer rate; represented
Jabar etal.
1.6
27
therefore integration of Equation (5) gives:
1.4
log (Ye - Yt)
1.2
ln W e = C
1
40°C 40 oC
0.8
45 oC 45°C 50 oC 50°C
0.6
55 oC 55°C
0.4
60 oC 60°C
0.2 0
0
1
2
3
4
-0.2
Time (h)
Slope (h-1) -0.566 -0.609 -0.683 -0.691 -0.718
mathematically as follows: dW e/dt = K.A (Ce – Ct)
ln (W e - W t) = ln W e - K.a (t)
(7)
Equation (7) can be rearranged so that it can be written in terms of percentage yield per mass of T. peruviana seed. (8)
Where Ye and Yt are the percentage yield of T. peruviana oil in bulk liquid at equilibrium and time t per mass of T. peruviana seed. Therefore, a plot of log (Ye - Yt) against time t (Figure 1) is a linear graph with slope equal to volumetric mass transfer rate coefficient K.a (Table 2) and intercept equal to log of the percentage yield of T. peruviana oil in bulk liquid at equilibrium (log Ye), that was used to determine Ye(cal.). Table 3 shows that pseudo first-order kinetic model did not fit the T. peruviana oil extraction kinetic process, because Ye calculated >> Ye experimental and at 55 and 60°C Ye calculated > 100%. This indicates that another kinetic model is needed to treat the T. peruviana oil extraction experimental data.
Table 2. Intercept and slope of pseudo first-order graph.
Intercept (log) 1.785 1.900 1.915 2.060 2.125
At any time t, W e and W t are the mass of the T. peruviana oil in organic solvent at equilibrium (g) and at time t (g) respectively. Therefore, Equations (5) and (6) become:
log (Ye - Yt) = log Ye – K.a(t)/2.303
Figure 1. Graph of pseudo first-order kinetic.
Temp. (K) 313 318 323 328 333
(6)
(1)
Where, dW e/dt is the mass transfer rate of T. peruviana oil (g/h), Ce and Ct are the concentration of T. peruviana oil in organic solvent at equilibrium (g/L) and at time t (h) respectively, K is mass transfer rate coefficient (h-1) and A is the surface area (m2) for mass transfer process. In the batch extraction process carried out, the volume of the extracting solvent was assumed to be constant, therefore;
The second kinetic model The second kinetic model called pseudo second-order extraction kinetic states that the rate of T. peruviana oil extraction from its oil bearing seeds is directly proportional to the square of oil yield. dW e/dt = K (W e - W t)2
(9)
dW e/dt = K. A/V (W e - W t)
(2)
dW e/dt = K.a (W e - W t)
(3)
Where, K is the volumetric mass transfer rate coefficient (h-1) of pseudo second-order extraction kinetic. Integrating Equation (9) with boundary condition; time t = 0, the mass of T. peruviana oil in bulk liquid is zero, We = 0, at the beginning of the extraction process. This gives:
ʃ dW e = K.a ʃ(W e - W t) dt
(4)
t/(W e – W t) = 1/W e + Kt
ln W e = ln(W e - W t) K.a t + C
(5)
Equation (10) can be rearranged so that it can be written in a linear form and in terms of percentage yield per mass of T. peruviana seed.
Where K.a is the volumetric mass transfer rate coefficient, while W e and W t are the mass of the T. peruviana oil in organic solvent at equilibrium (g) and at time t (g) respectively. At the beginning of the extraction process, time t = 0, the mass of T. peruviana oil in bulk liquid is zero, W e = 0,
2
t/Yt = 1/KY e + t/Ye
(10)
(11)
The slope and intercept (Table 4) of the plot of t/Yt versus t (Figure 2) can be used to calculate the percentage oil
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Table 3. Pseudo first-order volumetric mass transfer rate coefficient K.a and oil yield Ye.
Temp. (K) 313 318 323 328 333
-1
Intercept (log) 61.0 79.4 82.2 114.8 133.4
Slope (h ) 45.9 1.303 50.1 1.402 54.8 1.573 58.1 1.592 62.2 1.653
extraction of T. peruviana oil from its oil bearing seeds using petroleum ether as extracting solvent in soxhlet extraction method can be determined using second law of thermodynamic equations. ∆G = ∆H - T∆S
(12)
∆G = -RT lnKo
(13)
Equating Equations (12) and (13) gives Equation
(14)
logKo = (∆S/2.303R) - (∆H/2.303RT)
(14)
Ko = YL/Ys
(15)
Table 4. Intercept and slope of pseudo second-order graph.
Temp. (K) 313 318 323 328 333
Intercept (h) 0.0120 0.0100 0.0090 0.0075 0.0063
Slope 0.022 0.020 0.018 0.017 0.016
0.1
0.09 0.08
0.07
4040°C oC
t/qt (h)
0.06
4545°C oC
0.05
5050°C oC
0.04
5555°C oC
0.03
6060°C oC
0.02
0.01 0 0
1
2
3
4
5
Where, Ko is equilibrium constant, YL is percentage yield of T. peruviana oil at equilibrium temperature, Ys is percentage T. peruviana cake left after extraction (per mass of initial T. peruviana seed) at equilibrium temperature, R is gas constant, while ∆H, ∆S and ∆G are enthalpy, entropy and free energy of extraction respectively. The value of Ko and ∆G for extraction of T. peruviana oil using petroleum ether as extracting solvent were determined using Equations (15) and (12) respectively and are given in Table 6, while correlation coefficient of extraction process R2 was gotten to be 0.9912 from Figure 3. The values of enthalpy and entropy of extraction of T. peruviana oil from its oil bearing seeds are gotten from the slope (1525 K) and intercept (4.7967) of Van’t Hoff plot (Figure 3) to be 29.20 and 91.84 Jmol -1 respectively. The correlation coefficient of extraction process R 2 being equal to 0.9912 showed that extraction process fitted well with the obtained thermodynamic data, positive values of enthalpy and entropy of extraction indicated that the extraction process was endothermic and spontaneous respectively while the negative values of free energy indicated that the extraction process were feasible and irreversible.
Time (h)
Figure 2. Pseudo second-order graph.
yield Ye(cal) and pseudo second-order volumetric mass transfer rate coefficient K respectively. Table 5 shows that pseudo second-order kinetic model fitted the T. peruviana oil extraction kinetic process, because Ye calculated ≈ Ye experimental and volumetric mass transfer rate coefficient K ≈ 0.04 h-1 in all the extraction temperature. Extraction thermodynamics Thermodynamics parameters (∆H, ∆S and ∆G) for
Conclusions High percentage yield, abundance, biodegradability, renewability, and environmental friendly nature of the T. peruviana oil make it a not yet discovered potential alternative to petrochemical resource in industrial production of paint, varnish, biodiesel as diesel engine fuel, insecticides that brings about reduction in insects born disease in the community, soap, cosmetics, polyol and resin just to mention a few. Its inedible nature has a potential of facing out the use of edible oil as precursor in chemical industry, where by promoting food security, in an emerging economy like Nigeria. The soxhlet extraction process fitted well with pseudo second-order kinetic, the negative value of free energy, positive values of enthalpy and entropy of extraction indicated that the extraction
Jabar etal.
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Table 5. Pseudo second-order volumetric mass transfer rate coefficient K and oil yield Ye.
Temp. (K) 313 318 323 328 333
Ye cal. 45.7 50.0 55.0 58.6 62.3
Ye exp. 45.9 50.1 54.8 58.1 62.2
-1
K (h ) 0.040 0.041 0.037 0.039 0.042
Table 6. Equilibrium constant and thermodynamic parameters of T. peruviana oil extraction using petroleum ether.
Temp. (K) 313 318 323 328 333
1/T x 10-3 (K-1) 3.19 3.14 3.10 3.05 3.00
K 0.85 1.00 1.21 1.39 1.65
Log Ko -0.071 0.000 0.088 0.143 0.217
Figure 3. Van’t hoff graph.
process was irreversible, endothermic and spontaneous. Cold extraction of the T. peruviana oil gave high quality and oil yield with a low production cost when compare with extraction at high temperature (soxhlet extraction). Therefore, cold extraction method is better than soxhlet extraction method, in term of oil yield and quality. Conflict of Interest The authors have not declared any conflict of interest. REFERENCES Sahoo NK, Pradhan SR, Pradhan C, Naik SN (2009). Physical properties of fruit and kernel of Thevetia peruviana J. A Potential Biofuel Plant. Int. Agrophys. 23:199-204. Usman LA, Oluwaniyi OO, Ibiyemi SA, Muhammed NO, Ameen OM (2009). The potential of oleander (Thevetia peruviana) in African agricultural and industrial development: A case study of Nigeria. J. Afr. Biosci. 24:1477- 1487. Ibiyemi SA, Fadipe VO, Akinremi OO, Bako SS (2002). Variation in oil
ΔG0 (J/mol) 454.08 -5.12 -464.32 -923.52 -1382.72
ΔH0 (KJ/mol) 29.20 29.20 29.20 29.20 29.20
ΔS0 (J/mol) 91.84 91.84 91.84 91.84 91.84
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